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1974 850 commando trouble SOLVED

Discussion in 'Norton Commando Motorcycles (Classic)' started by krullbeast, Aug 13, 2018.

  1. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    Woe is me. I tried limping my norton home yesterday on one cylinder and i didn't make it. I broke down, hid my bike in the woods and hitchhiked home. Has anyone ever lost power on one side, which was backfiring a bit. I had power at the very bottom of my throttle, so when i got up to speed downhill it would sputter and feel like it was firing because it gave short burst of power, but as soon as i started up a hill it would bog down and i'd have to downshift and go 40 mph over hills. The left side has spark, is getting gas and a compression test read 90 on that side. the choke cable is a little worn on that side and it hangs down when fully off about less than a 1/4 inch because i stuck my finger through the velocity stack side and felt them. it isn't much different, that being said. Does anyone have any advice? Has this happened to you? what was the solution, if so? Thank you for your time.
    Lee
     
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  2. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    also, i'm running a tri spark ignition system and i have the new 930 amals. thanks!
     
  3. rvich

    rvich VIP MEMBER

    Joined:
    Jul 25, 2009
    I wonder if your needle fell out of its holder in one carb.
     
  4. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    they were both in there. do you mean slipped a notch or completely fell out? thanks
     
  5. Adam_R

    Adam_R

    Joined:
    Nov 20, 2015
    what plugs are you running?
    and what jets in carbs?
    i had this happen to me but solved with new plugs and different needle jets
     
  6. lazyeye6

    lazyeye6 VIP MEMBER

    Joined:
    Feb 28, 2014
    I had similar situations on 2 of my bikes. Once the main jet in one carb partially unscrewed itself. Another time one of
    the Lucas coils simply failed. Another time the circlip on one of the carb needles popped off and the needle
    would not raise and lower as it should. And, as I'm sure has happened to many others, one spark plug fouled
    and would not fire correctly under load.

    90# compression is not normal!!!! Do that test again with the throttle wide open . It should be more like 150#
    While a TriSpark ignition should work with a low battery, I would check that the battery is fully charged.

    Report back after examining these things.
     
  7. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    i run NGK BP7ES plugs and i believe 32 mm with 220 main jets
     
  8. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    also, it ran great up until it didn't (happened suddenly) and then i tried limping it on one side and it shut down completely and had more than normal oil from the head area on the left chain case. it always drips oil obviously, i put the dyno dave clutch rod sealer in there last year, but it also has a small primary leak. these i believe are unrelated except for the oil, maybe?
     
  9. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    thank you i will! i hope it's not the head dangit. battery tested good. fully charged
     
  10. rvich

    rvich VIP MEMBER

    Joined:
    Jul 25, 2009
    It could be either one, but if the clip comes off the needle just sits in the jet even tho the slide moves up. It plays havoc with one side if the other side is normal.
     
  11. 1up3down

    1up3down

    Joined:
    Jan 12, 2011
    i run NGK BP7ES plugs and i believe 32 mm with 220 main jets

    ---------------

    With an electronic ignition like a TriSpark you have to have something in the sequence be resister
    such as NGK BPR7ES (resister) plugs, or dedicated resister plug wires, do you have such?

    did you pull the spark plug on the non firing side just to see if it badly fouled, just a thought

    ok with both plugs checked and clean and new pull them out and ground them firmly on the head while you kick it over in a dark garage, do you see both sparking? if not you have an electrical issue and not a carb one....
    if which case it could be as simple as a fractured plug wire, swamp them to each side and see if that makes
    that other side not fire? do you still have the two original coils? consider getting the single 12 volt from CNW
     
    Last edited: Aug 13, 2018
  12. krullbeast

    krullbeast

    Joined:
    Apr 18, 2017
    thank you. i do not have resister plugs, i believe my resister plug wires are correct, i have new twin coils that were recommended by trispark, and yes the bad side was pretty fouled out (quickly, as i replaced and checked again) yes both spark. and the left side is getting gas through the carb. about to check on multiple scenarios, i appreciate it!
     
  13. Steves

    Steves

    Joined:
    Oct 16, 2016
    I think we have all been here at one time or another. I don't think resistor plugs or caps are suddenly going to be an issue. I would check the plugs see what they look like, put new ones in. Then I would check the carbs from filter to manifold to see if anything amiss. Once that is done start either with carbs or electrics and work your way through. If it is a sudden change it is probably an electrical problem unless you find something amiss with the carb in the first check above. It really is a process of elimination, resist the temptation to overthink it, probably something really simple.
     
  14. Beach

    Beach VIP MEMBER

    Joined:
    Aug 27, 2013
    I don't think it is ignition or the problem would be on both sides, since it's a wasted spark system(fires both plugs at same time). Try switching plug wires and see if problem moves to other cylinder. I would check carbs as mentioned and if all is ok there maybe a compression test.
     
  15. N0rt0nelectr@

    N0rt0nelectr@ VIP MEMBER

    Joined:
    Sep 15, 2014
    What coils are you running? Years ago I lost 1 coil while out on a ride, had to limp on home where I had a used coil and replaced it. Ran fine from that point on.

    John in Texas
     
  16. illf8ed

    illf8ed

    Joined:
    Dec 30, 2003
    If you have gas and spark the only thing left is compression. Take the valve covers off, kick through and make sure the valves are openning. After that a compression check. If all is good the spark plugs could still be suspect...replace them and see what happens.
     
  17. rvich

    rvich VIP MEMBER

    Joined:
    Jul 25, 2009
    The comment about more oil than normal on the primary chain case is worrisome. Usually a head should not leak enough oil to reach the chain case.
     
  18. nortonisthebest

    nortonisthebest

    Joined:
    Aug 1, 2014
    On my 1972 Norton I had a Sparx electronic ignition system in place of my points. My bike started missing out on one side causing it to run intermittently on one cylinder. I finally located the problem. All electronic ignitions stater plates have two coils wrapped with copper wire. One coil for the left cylinder and one for the right cylinder. I found the copper wire on one of the coils was broken. It would make contact ounce in a while and then separate causing the bike to malfunction. You might want to use an ohm meter to check for any broken copper winding's. On my bike I found one coil was loose causing the thin copper wire to brake.
     
  19. lazyeye6

    lazyeye6 VIP MEMBER

    Joined:
    Feb 28, 2014
    "All electronic ignitions stater plates have two coils wrapped with copper wire. One coil for the left cylinder and one for the right cylinder."

    AHEM! A flat earth statement if I ever heard one.
     
  20. nortonisthebest

    nortonisthebest

    Joined:
    Aug 1, 2014
    It looks like I need to clarify my statement. Every electronic ignition stator plant I have installed on my Norton's have had the two coils wrapped with copper wire. Weather they are called coils or some other name is beside the point. I am just trying to help.
     
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